Microsoft's March 2012 "Black Tuesday" announcement included the MS12-020 patch, which fixes a vulnerability in Microsoft's implementation of RDP. This vulnerability (CVE-2012-0002) could allow a remote unauthenticated attacker to execute arbitrary code on the affected system. Microsoft labeled this issue "Critical" and we assigned it our highest severity label "Patch Now" for servers. Here's why:

• The CVE-2012-0002 vulnerability applies to most flavors of Microsoft Windows.
• It can be exploited over the network.
• Companies often make RDP accessible on the standard TCP port 3389 from the Internet for remote access to servers and sometimes workstations.

These factors make it very attractive for attackers to attempt reverse-engineering Microsoft's MS12-020 patch to, understand the details of the bug and craft an exploit. This will likely happen sooner than 30 days. The universal applicability of the exploit and its targetability over the Internet and internal networks might motivate the creation auto-propagating worms to capture systems quickly and efficiently.

For these reasons, we recommend applying the MS12-020 patch as quickly as practical in your environment. Until you install the patch, consider moving your RDP listeners to non-standard ports. You should also explore the applicability of Microsoft's advice to enable Remote Desktop’s Network Level Authentication (NLA). This will mitigate the problem: "On systems with NLA enabled, the vulnerable code is still present and could potentially be exploited for code execution. However, NLA would require an attacker to first authenticate to the server before attempting to exploit the vulnerability."

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Lenny Zeltser
zeltser.com
@lennyzeltser